Illumination zoom system for microscopes

ABSTRACT

A microscope illumination system having a zoom unit located before the field diaphragm is useful to provide maximum illumination for objectives from 10 to 110X, when using a suitable condenser, without the disadvantages of other systems. The zoom unit comprises a positive lens, a negative lens and a positive lens in series with the two positive lenses connected together and movable with respect to the negative lens along the optical axis as a unit.

O United State 3,876,289

DeVeer et al. PM Apr. 8, 1975 [54] ILLUMINATION ZOOM SYSTEM FOR 3.051.052 8/1962 Bergstcin 350/!84 MICROSCOPES [75] Inventors; Johannes D. Deveer L Primary Examiner-Ronald L. Wibert Mass; Klaus p SchindL Vienna; Assistant E.\'umim'rConrad Clark Mois Demink, v d fl both f .-l!!urne Agem. 0r Firm-Alan H. Spencer: William Australia C. Nealon; Howard R. Berkenstock. Jr.

[73] Assignee: American Optical Corporation.

Southbridge. Mass. [57] ABSTRACT l Filed; Mar. 26. 1973 A microscope illumination system having a zoom unit [2|] Appl. No.: 345.047 located before the field diaphragm is useful to provide maximum illumination for objectives from l0 to to llOX, when using a suitable condenser. without the U.S. disadvantages of other systems The zoom uni com. Clprises a positive lens a negative lens and a positiyc [58] Field of Search 350/l84. 87 lens in series with the two posmw lenses Connccmd together and movable with respect to the negative lens References Clted along the optical axis as a unit.

UNlTED STATES PATENTS 2.078.586 4/1937 Richter 350/ix4 3 2 Drawing F'gures AD T5 U R9 \RIO I couoeussn ILLL'NHNATION Z()().\l SYSTEM FOR MICROSCOPES BACKGROUND OF THE l.\'\ii.\"l'l().\-

the field stop and diaphragm are adjusted over a wide range.

FlG. l is an optical diagram of a portion of a microscope illtnnination system. illustrating one eml'todiment of a zoom unit according to the present invention.

Zoom units in illumination systems are ery desirable 5 in order to properly fill the field and pupil for objec- FIG. 2 is a graph. demonstrating the optical compentives of varying powers. Microscopeshaving zoom units sation of the preferred embodiment. in the illumination systems are known. but suffer disad y I vantages frequently making them either undesirable. or Dl: rAlLhD DllSCRlP l Ol' l H l at best. of little advantage. The most common form of to The drawing is an optical diagram of a preferred form illumination system with a zoom has the field diaofthe present invention wherein A generally designates phragm located before the zoom. The principal disadthe zoom lens unit positioned in optical alignment invantage of this type of system is the \ery high quality termediate the light source (not shown) and field din of the optical system necessary to produce an image of phragm H). The zoom unit has three lens components the field diaphragm for interference contrast use. 15 designated ll. lll and l\. Component lll is a stationary further disadvantage of this type of system is that the optically aligned double concave negative singlet. optics necessary to provide proper reproduction of the Components ll and l\' are optically aligned double confield diaphragm se\erely restricts the L'\' light transvex singlets positioned on opposite sides ofthe stationmitted and prevents or significantly impairs fluorescent ary component having variable spaces. respectively S1 microscopy studies. 30 S2 and S3 S4. Components II and l\' are moved in Other forms of zoom units are known but generally unison along'the optical axis to provide a fully illumihave the disadvantage of not filling the entire field dianated field in the field diaphragm FD and extend the phragm with light and simultaneously extending the image 1- ofthe light source across the entire aperture diimage of the light source across the entire aperture diaaphragm AD. The aperture diaphragm referred to is phragm. A further disadvantage of prior art systems is near the front focal plane of the condenser. the utilization of uncompensated or mechanically com- The successive air spaces of the system are desigpensated zoom units. The former offers little advantage Hated l 55. respecti ely. 56 designates the distance to a microscope illumination system without any zoom from the center of the fixed component lll of the zoom and the mechanically compensated systems are co1tt unit to the plane ofthe intermediate image i of the light plex. delicate. and expensive to construct. source in the preferred embodiment. S8 designates the H distance between the center of fixed lens lll and the OB'lhC ls lHl: PRllSE\l llx l image ofthe field diaphragm FD projected through the It is one object ofthe present invention to provide a zoom unit. S7 designates the fixed distance between microscope illumination system having a zoom unit lomovable components ll and l\' of the zoom unit. Axial cated between the light source and the field diaphragm. 33 lens thicknesses are designated 'l'l T5. respectively lt is another object of the present invention to proand successive radii of curvature are designated Rl vide a zoom unit having an illumination system which R10. respectively. where the minus sign applies to stlt fills the field diaphragm with light and sitnultaneously faces whose center of curvature lies on the field diaextends the image of the light source across the entire phragm side of their vertices. The refractive indices aperture diaphragm. 4t and Abbe number ofthe glasses in the successive lenses It is another object of the present invention to proare designated NDl to NDS and VI to 1/5. respectively. vide an optically compensated zoom unit in a micro- In the table below. system values are presented for scope illumination system. the preferred embodiment of the present invention.

It is still a further object of the present invention to Thicknesses. radii and distances are in millimeters. The provide an optically compensated zoom unit located at 4) values of collector system element 1 and telescope lens the image of the light source and between the light are not an essential part ofthe present invention and source and field diaphragm. those skilled in the art are capable of any necessary modifications to adapt the same to conventional micro- BRlEF DFSCRllTnON 9 THE l Eh l i0 scope illutninationsystems. I I

A zoom umt having positive-negative-positive lens A system according to the present invention will proclements. with the negative element being fixed and the vide a zoom range of about 1 to 8X. Although a zoom positive elements being rigidly connected and slidable of only I to 4X is necessary to fill the pupil of a 10X along the optical axis which is located between the light 0.32NA objective and a lOOX 1.32NA objective from source and field diaphragm permits the field diaphragm sq a filament illumination source. the additional zoom to be filled with light and the image of the light source range enables one to use the same zoom system to fill to extend across the entire aperture diaphragm when the entire pupil with a hot spot of a gas discharge lamp.

REFRACTXVE ABBE RADIUS THICKNESS INDEX SPACE NUMBER R 'r ND 5 y R 81.092 l T 31) ND 1.50378l y, =66.92

S|=3.0O to 49.34 R.=-51 035 v n T. 8.0 ND 1.503781 =66.92

Continued REFRACTIVE ABBE RADIL'S THICKNESS INDEX SPACE NLMBER R T ND 5 lll T;I 2.5 ND; 1.636359 y =35.34

R, =-35i-Ho s ,=3.oo to 49.34 R =5 L035 7 iv R, 51.035 so ND, 151mm 7, =6o.92

S.=i:7i:4 to sumo R =x-w26 v T 4.0 Ni), LSIhXll 'y =64 ]7 Rm x s,-' h2 .x s =le7i27 Referring now to FIG. 2. the abscissa is in millimeter units and represents the distance of the positive ele- THiCK- REFRACTIVE ABBE ment and the ordinate fixed negative element in the RAEIUS 2 SS SPACE NUMBER zoom unit plotted against the vertical axis in millimey ters to show deviation from the image of the field dia- R1.=5lio35 phragni FD projected through the zoom system alone n O NOEL-03731 73:66 in the direction of the light source. The minimal devia- 1g i tion. slightly over I millimeter and the plurality of preto 3.00

- .i, R,-,=35.4l6 Clbt. alignment points clearly demonstrate the optical m TEN NDFIMMSQ y3=3534 compensation of the preferred embodiment. [LP-354m What is claimed is: 3

to 1. ln a transmitted light microscope illumination sys- Rr= 5l 035 tem having a light source. an ad ustable field dia- Iv T,.=x.o ND =l.5()378l 4=6692 phragm. an adjustable aperture stop and a condenser REM-035 having a front focal plane all in optical alignment along 5' an llXlS. the ad ustable aperture stop being positioned S,,=-36 near the front focal plane. the improvement comprising 3S an optically compensated zoom unit consisting of positive-negative-positive lens elements. said negative lens element being fixed in position and said positive elements being rigidly coupled and axially movable said zoom unit being located between the light source and field diaphragm. an intermediate image of said light source being located between the fixed element of I said zoom and said field diaphragm, said zoom unit having a substantially stationary back field diaphragm image plane such that the adjustable field diaphragm is filled with light when said aperture stop and said field diaphragm are varied over a wide range and an image of the light source extends completely across the adjustable aperture stop at all positions of adjustment.

2. The improvement of claim 1 wherein lens radii (R), thicknesses (T), and spacings (S) are expressed in millimeters and a negative sign indicates lens radii on centers of curvature on the field diaphragm side of said lens:

3. The improvement of claim 2 further including a collector lens and telescope lens having the values set forth in the following table: 

1. In a transmitted light microscope illumination system having a light source, an adjustable field diaphragm, an adjustable aperture stop and a condenser having a front focal plane all in optical alignment along an axis, the adjustable aperture stop being positioned near the front focal plane, the improvement comprising an optically compensated zoom unit consisting of positive-negative-positive lens elements, said negative lens element being fixed in position and said positive elements being rigidly coupled and axially movable, said zoom unit being located between the light source and field diaphragm, an intermediate image of said light source being located between the fixed element of said zoom and said field diaphragm, said zoom unit having a substantially stationary back field diaphragm image plane such that the adjustable field diaphragm is filled with light when said aperture stop and said field diaphragm are varied over a wide range and an image of the light source extends completely across the adjustable aperture stop at all positions of adjustment.
 2. The improvement of claim 1 wherein lens radii (R), thicknesses (T), and spacings (S) are expressed in millimeters and a negative sign indicates lens radii on centers of curvature on the field diaphragm side of said lens:
 3. The improvement of claim 2 further including a collector lens and telescope lens having the values set forth in the following table: 